Airway constriction and inflammation are key components of asthma and anaphylaxis. This research aims to improve our understanding of the pathogenesis of these responses, and to identify more effective means of their modulation or prevention, using the neuropeptide vasoactive intestinal peptide (VIP) as a prototype test drug. Specific Aims: 1) Test the hypothesis that VIP is an endogenous modulator of airway constriction; 2) Test the hypothesis that VIP is an endogenous modulator of airway inflammation; 3) Test the hypothesis that VIP suppresses inflammation by a dual action-suppressing inflammatory cell activity and inhibiting NF-kappaB activation and consequent production of inflammatory cytokines; and 4) Test the hypothesis that VIP's actions are mediated by VPAC1 and VPAC2 receptors and resultant stimulation of the adenylate cyclase/protein kinase A (PKA) pathway. These aims will be tested in 2 models of airway constriction and inflammation, induced by anaphylaxis and by capsaicin, in isolated lungs and in vivo. The animals will be wild-type mice and mice with overexpression of VPAC1 and VPAC2 receptor, or with targeted deletion of the VIP gene (VIPKO) or of the VPAC1 or VPAC2 receptor (VPACKO). For Aim 1, we expect to determine that airway constriction induced by specific stimuli is alleviated in mice with overexpression of VIP receptors, and exaggerated in VIPKO or VPACKO mice, and that catalytic antibodies against VIP enhance airway constriction. For Aim 2, we expect to show that VIP is released in response to airway inflammation, and that airway inflammation is reduced in mice with overexpression of either of the 2 VIP receptors, and exaggerated in VPACKO mice or by catalytic antibodies against VIP. For Aim 3, we will seek evidence that VIP suppresses inflammatory cell accumulation in the airways of late-phase asthma models, and inhibits NF-kappaB activation and consequent production of inflammatory cytokines and chemokines. For Aim 4, the dominant receptors will be identified by testing the effects of selective VPAC1 and VPAC2 receptor agonists and by use of VPAC transgenic mice, and the importance of the postulated signal transduction pathway will be assessed by measuring VIP-induced cyclic AMP production and PKA activation, and the extent to which PKA inhibitors reduce the modulatory influence of VIP on airway constriction and inflammation. Significance: The knowledge gained from these studies should provide insights into the mechanisms of asthmatic/anaphylactic responses and may suggest new therapeutic options for these conditions.